DESCRIPTION (adapted from the applicants' abstract) The long-term goal of this project is to further the understanding of how emotional factors influence sleep. Emotional state has a strong influence on sleep quality and amount. This statement can be attested to by almost everyone, and it is factually supported by the observed role of emotional factors in human sleep medicine, particularly sleep disorders related to a psychiatric condition. However, the role of emotion has virtually been ignored in basic sleep research, possibly because of the lack of a clear anatomical focus, or perhaps because of a lack of established models. It is now becoming increasingly apparent that the amygdala, the limbic center of emotion, has a strong modulatory role in the control of sleep. Inbred mouse strains are being examined in order to find models of anxiety and mood disorders. The investigators plan to study sleep in inbred mouse strains with differences in emotional reactivity in order to begin to understand how genetics and the environment interact in producing the effects of emotion on sleep. The investigators' strategy is to : 1) establish protocols for studying how emotion affects sleep in inbred mouse strains, 2) identify the anatomical regions that could account for strain differences in emotional reactivity as it affects sleep, and 3) determine the functional significance of these regions in the control of emotion and sleep. To accomplish these goals, the investigators will examine the effect of fear conditioning on sleep, identify the activated brain areas that affect sleep and examine the function of these regions by selectively preventing their activation in response to fear conditioning. These studies will help elucidate into how stress, emotion and environmental factors influence sleep. This work will advance the understanding of how stress and anxiety affect sleep and may give insight into sleep disorders such as insomnia and into mental disorders in which sleep is affected. The investigators findings may be especially relevant to posttraumatic stress disorder (PTSD), which is typically characterized by a prominent sleep disturbance in the aftermath of exposure to a psychologically traumatic stressor.